by Dan Roberts
October 12, 1999
Retinal cell transplantation involves transplanting retinal pigment epithelium (RPE) cells from a healthy eye (preferably fetal tissue). Experimentation has been carried out since 1997 at Barnes Hospital in St. Louis, the University of Chicago, and other locations, but the most important success so far has only been conquering the problem of rejection. The eye does not naturally try to reject photo receptor cells, but it tends to do so with RPE cells, because of their proximity to the blood supply of the choroid layer. So far, however, immunosuppressive drugs have been successful in counteracting this. One of these drugs, the steroid prednisone, is used only when necessary for blocking transplant rejection, since it has been found to cause complications.
In the beginning, there was also a problem with retinal detachment following transplant surgery, due to the size of the instruments used. New procedures, however, seem to be correcting the problem, with the procedure having been performed successfully on several patients. In spite of these successes there have not yet been reports of significant improvement in any area of the subjects' vision. These areas include visual field, dark adaptation threshold, contrast sensitivity, reading speed, mauloscope ERG, and acuity on the Snellen chart. More time is needed for further observation before any conclusions can be drawn.
In a related study, a research team at England's Institute of Ophthalmology has reported actually improving vision in animal models with inherited retinal degeneration through cell transplantation. Professor Ray Lund headed up the experiment, which involved taking cells from nerves in the legs of rats and injecting them into the its own retina. Application of this procedure to humans has yet to be attempted.
For further information, see the MD Support Glossary and read the dicussion "Retinal Transplantation" in the Clinic